I'm pretty sure he doesn't have an Envoy or Trailblazer. In his first post he states that it is a 4.3L V-6, Envoys and Trailblazers have either a 4.2L I-6, or a 5.3L V-8.Is it throwing any check engine codes? These have been known for condensation building up on the AC lines and dripping down onto the distributor.